The invention is based on a brake booster. A brake booster of this kind is known (German Offenlegungsschrift No. 28 25 087).
A brake booster of this kind is equipped with an integrated anti-skid system, so that the brake booster has a dual function, that is, boosting braking action and modulating pressure for the anti-skid system. To modulate pressure, a separate valve circuit is used together with a special type of brake booster, in which the main cylinder is used for pressure modulation.
However, other systems are also known, which operate according to the principle of direct feeding of pressure from the pressure supply means (German Offenlegungsschrift No. 32 37 959).
These known types have devices with which, if the pressure supply means fails, the piston of the main cylinder is retained in a specific position, so that a safety range for operation of the piston stroke is still available.